Multimedia backwashable filtration system

ABSTRACT

A multimedia fluid treatment unit and rotatable valve are disclosed in which a plurality of discreet containers are removably stacked upon each other and contain various different and distinct water treating media. The rotatable valve is rotatable between either of three positions one of which is a service position for routing the water to be treated through the unit for treatment, a second of which is a rinse position for rinsing the media in the unit, and a third of which is a backwash position for backwashing and/or regenerating the media.

This application is a division of application Ser. No. 09/025,231, filedFeb. 18, 1998 now U.S. Pat. No. 6,254,772, which application is acontinuation-in-part of application Ser. No. 09/007,497, filed Jan. 15,1998 abandoned.

BACKGROUND AND SUMMARY OF INVENTION

The present invention is directed to a multimedia backwashable filtersystem and, more particularly, to a multimedia water treatment unit androtatable control valve therefor.

Multimedia fluid treatment systems have been employed in the past forthe treatment of various fluids, such as water. In these systems,various different treatment media have been employed in serialrelationship to each other so that for example one medium may have abeneficial effect on subsequent downstream media. For example, inHeskett U.S. Pat. No. 5,415,770 it is disclosed that the use of certainfinely divided metals, such as alloys of copper and zinc, may beemployed as an upstream treatment medium to remove certain chemicalconstituents, such as residual chlorine, prior to subjecting water toother downstream water treatment media, such as activated carbon and/oran ion exchange medium. By removing the chlorine, the function and lifeof the latter two media may be improved and extended.

In such prior systems the several respective media are frequentlylocated in several distinct units which are physically separated fromeach other and the fluids are passed through these distinct units in aserial fashion. These individual units can be individually serviced butthey are demanding of space and material. Where the several respectivemedia are contained in a single container or tank, they are difficult tomaintain separate from each other, particularly due to the widedisparity in weights and/or sizes of media particles. Even where theycan be maintained separate from each other, the placement of each of themedia in the same tank makes it physically difficult to service orreplace one medium without replacing the others due to their positioningrelative to each other. Another disadvantage, particularly in smallcountertop water treatment units, is that no provision is currentlyknown to permit rinsing or backwashing of the media which, if possible,might greatly extend the life of the system and their respective media.

It is the purpose of the present invention to avoid and eliminate theaforementioned disadvantages. In the present invention, a multimediafluid treatment unit with an efficient rotatable control valve isprovided which is compact, permits ready servicing of the unit and theutilization of a number of different media in the unit, and whichprolongs the life of the unit by selective arrangement of the severalmedia relative to each other to remove compounds which might be harmfulto some of the media and by permitting rinsing and backwashing of theseveral media. Moreover, in the present invention a plurality of mediacontaining containers are provided which are removably fixed to eachother to facilitate replacement and service.

In one principal aspect of the present invention, a multimedia fluidtreatment unit comprises a plurality of discrete containers stacked uponeach other. Each of the discrete containers has an inlet for fluid atone location thereon and a discharge for fluid opposite the inlet. Eachcontainer is positioned in series flow relationship to the next adjacentcontainer, and each of the containers defines a chamber for receivingand retaining a finely divided fluid treatment medium therein andbetween the fluid inlet and discharge whereby the fluid to be treatedwill flow through the medium in each chamber and serially to the mediumin the next chamber. A valve is associated with the containers and isoperable to a first service position in which the fluid to be treated isintroduced to the containers and the fluid which is treated by the mediain the containers is removed from the containers and discharged, to asecond rinse position in which the treatment medium in the chambers isrinsed, and to a third backwash position in which the treatment mediumin the chambers is backwashed.

In another principal aspect of the present invention, each of thecontainers includes a floor which includes perforations therein to formthe discharge and contain the medium in the chamber of the container.

In still another principal aspect of the present invention, a meshmaterial is supported on the floor to contain the medium in the chamberof the container.

In still another principal aspect of the present invention, each of thecontainers is removably attached to its next adjacent container.

In still another principal aspect of the present invention, the fluidtreatment medium is a water treatment medium which may be two or more offinely divided metals or alloys thereof, activated carbon, inertparticulates and/or ion exchange media.

In still another principal aspect of the present invention, a housinghas an elongate cylindrical chamber therein, and first, second, thirdand fourth passages extending through the housing and communicating withthe cylindrical chamber. A valve includes a cylindrical valve bodymounted for rotation in the cylindrical chamber, and the valve body hasan axially extending passage therein which communicates with a source offluid supply for the valve. The valve body has a first area adjacent itscylindrical surface which is aligned with the first and fourth passages,and a second area also adjacent its cylindrical surface which is alignedwith the second and third passages. The valve body also includes firstand second ports communicating between the axially extending passage andthe first area, and a third port communicating between the axiallyextending passage and the second area. The cylindrical valve body isselectively rotatable between the first service position in which thefirst port communicates with the first passage and the second passagecommunicates with the third passage, the second rinse position in whichthe second port communicates with the first passage, and the thirdbackwash position in which the third port communicates with the secondpassage and the first passage communicates with the fourth passage.

In still another principal aspect of the present invention, theaforementioned housing includes fifth and sixth passages extendingthrough the housing and communicating with the cylindrical chamber, andthe cylindrical valve body has a third area adjacent its surface whichis aligned with the fifth and sixth passages, and fourth and fifth portscommunicating between the axially extending passage and the third area.The fifth passage communicates with the fourth port when the cylindricalvalve body has been rotated to the second rinse position, and the sixthpassage communicates with the fifth port when the cylindrical valve bodyhas been rotated to the third backwash position.

In still another principal aspect of the present invention, theaforementioned housing includes a seventh passage extending through thehousing and communicating with the first area, and the first area isaligned with the seventh passage so that the seventh passagecommunicates with the fourth passage when the cylindrical valve body hasbeen rotated to the second rinse position.

In still another principal aspect of the present invention, themultimedia fluid treatment unit includes sediment retaining meansadjacent the discharge of the most downstream container when the valveis in the first service position for retaining fine particles which mayhave passed through the chambers of the containers during the treatmentof the fluid. The aforementioned seventh passage communicates with thefourth passage to discharge such fine particles from the sedimentretaining means when the valve is positioned in the second rinseposition.

In still another principal aspect of the present invention, themultimedia fluid treatment unit includes at least one fluid treatmentmedium which is an ion exchange medium and a container for theproduction and containment of a fluid composition for the regenerationof the ion exchange medium. The fifth and sixth passages communicatewith the last mentioned container to introduce fluid to and dischargefluid from the container.

In still another principal aspect of the present invention, theaforementioned seventh passage defines an overflow for the container forthe composition and communicates with the first area, the first area isaligned with the seventh passage, and the seventh passage communicateswith the fourth passage when the cylindrical valve body has been rotatedto the second rinse position.

In still another principal aspect of the present invention, theaforementioned second passage is sealed when the cylindrical valve bodyis rotated to the second rinse position, the fifth and sixth passagesare sealed when the cylindrical valve body is rotated to the firstservice position, the sixth passage is sealed when the cylindrical valvebody is rotated to the second rinse position, the fifth passage issealed when the cylindrical valve body is rotated to the third backwashposition, and the aforementioned seventh passage is sealed when thecylinder is rotated to the first and third positions.

In still another principal aspect of the present invention, theaforementioned sealing is by a seal on the surface of the valve body inthe second area which aligns with the second passage when the valve bodyis rotated, by seals on the surface of the valve body in the third areawhich align with the fifth and sixth passages when the valve body isrotated, and by a seal on the surface of the valve body in the firstarea which aligns with the seventh passage when the valve body isrotated.

In still another principal aspect of the present invention, the surfaceof the cylindrical valve body in the first and second areas is spacedfrom the surface of the chamber in the housing to define an annularpassage between the surfaces, and the first, second and third areas aredivided from each other to define first and second annular passages atthe first and second areas respectively.

In still another principal aspect of the present invention, the first,second and third areas are divided from each other by O-rings about thecylindrical valve body to define the first and second annular passages.

In still another principal aspect of the present invention, thecylindrical valve body comprises a single cylinder.

These and other objects, features and advantages of the presentinvention will be more clearly understood through a consideration of thefollowing detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

In the course of this description, reference will frequently be made tothe attached drawings in which:

FIG. 1 is an overall, partially broken, cross-sectioned elevation viewof a preferred embodiment of multimedia fluid treatment unit androtatable valve incorporating the principles of the present inventionand with the valve positioned in the service position;

FIG. 2 is a broken, cross-sectioned elevation view of the unit and valveshown in FIG. 1, but with the valve positioned in the rinse position;

FIG. 3 is a broken, cross-sectioned elevation view of the unit and valveshown in FIG. 1, but with the valve shown in the backwash position; and

FIG. 4 is an exploded perspective view of a preferred embodiment ofvalve housing and valve of the present invention and showing the valvecomponents in their service position in FIG. 4A, their rinse position inFIG. 4B and their backwash position in FIG. 4C.

DESCRIPTION OF THE PREFERRED EMBODIMENT

A multimedia fluid treatment unit 10 is shown in FIGS. 1-3. In apreferred application, the unit 10 may be a countertop or under thecounter unit for the treatment of municipal or other potable watersupply. The unit 10 preferably comprises a plurality of containers 12,13, 14 and 15 as shown in FIG. 1. In order to simplify inventoryconsiderations, each of the containers 12, 13, 14 and 15 is preferablyidentical in design, and therefore, in the description to follow like orsimilar container components will be assigned like reference numerals.

Each container comprises a vertical sidewall 16 and a floor 18 havingperforations 20 for the discharge of treated water from the respectivecontainers, as shown by the arrows in FIG. 1. The sidewall 16 and floor18 of each of the containers define a chamber 21 in each for containingwater treatment media as will be described more fully below. The floor18 of each container preferably functions as support for a mesh or fibermaterial 22 which has a pore size which is small enough to contain thewater treating medium in each of the respective container chambers 21,but large enough to permit the water to pass through the mesh and bedischarged from each respective container. By way of example, the meshsize of the mesh 22 may be about 10 microns. Each of the containers 12,13, 14 and 15 also includes threads 24 at their top and a downwardlyextending flange 26 at their bottom having internal threads 28 which areadapted to thread onto the threads 24 at the top of the next lowercontainer to readily permit assembly of the containers in serialrelationship to each other, as seen in FIG. 1, and also disassembly whendesired for example for servicing or replacement.

In the preferred embodiment as shown in the drawings, the unit 10 alsoincludes a riser conduit 30 upon which the respective containers areassembled, with the floor 18 of each container having an opening toreceive the riser and an O-ring 32 to prevent undesirable leakagebetween the respective containers at the riser 30. An O-ring 33 is alsoprovided between the sidewalls 16 of each of the respective containersto seal them against leakage to their exterior.

The unit 10 is preferably capped by top piece 34, which may for examplebe a shortened version of the containers 12, 13, 14 and 15. The toppiece 34 provides sufficient space for the water to be treated to bedischarged at the top of the riser 30, as shown by the arrows in FIG. 1,and to flow down through the respective containers for treatment. Likethe containers 12, 13, 14 and 15, the top piece 34 also preferablyincludes a floor 18 having perforations 20 which supports a mesh 36thereon. The mesh 36 is preferably of finer mesh than the mesh 22 on thefloors 18 of the containers, and is for example 0.5 micron. The mesh 36is finer because it has the purpose of retaining any fine contaminateparticles which might enter with the water to be treated. The top piece34 also preferably includes threads 24 for receiving a closure cap 38having a downwardly extending flange 39 which is threaded onto thethreads 24 of the uppermost container 12, also as seen in FIG. 1. Thus,it will be seen that the mesh 36 is accessible for servicing andreplacement simply by removal of the closure cap 38 if desired.

The unit 10 of the preferred embodiment of invention also includes avalve housing 40 having an upwardly facing well 42 defined by anupwardly extending flange 44 having threads 46 at its top for receivingand attaching the threaded flange 26 of the bottommost container 15.

The chamber 21 in each of the respective containers 12, 13, 14 and 15 inthe unit 10 preferably contains different fluid treatment media. Forexample where the unit is to be utilized to treat water, the watertreatment medium A in the chamber 31 of container 12 may be aparticulate filter material, such as sand. The water treatment medium Bin container 13 may be a finely divided metal, such as disclosed in thepreviously mentioned U.S. Pat. No. 5,415,770. The water treatment mediumC in container 14 may be some sort of ion exchange resin for the removalof undesirable ions such as a cationic resin for the removal ofhardness, or an anionic resin for the removal of undesirable nitrates ororganics. The water treatment medium D in container 15 may be activatedcarbon. Because each of the containers are removably attached to eachother, servicing and replacement of the respective media arefacilitated. Moreover, in the arrangement of the media described, theparticulate or finely divided metal medium B can actually prolong thelife of an ion exchange medium C and/or activated carbon medium D byremoving residual chlorine from the water which may have a deleteriouseffect on either of the latter two media.

A floor plate 48 is also preferably positioned in the well 42intermediate of the depth of the well 42. As best seen in FIG. 4, thefloor plate 48 may rest on a shoulder 50 in the well. The floor plate 48also preferably includes an O-ring 32 to seal against leakage between itand the riser. The floor plate 48 provides a support for a very finemesh 54 on the top of the floor plate, and has perforations 52 to permitthe passage of water therethrough, as shown by the arrows in FIGS. 1 and3. The mesh 54 is preferably fine and on the order of 0.5 micron and hasthe purpose of retaining any extremely small fines that may be able tomake their way through the respective media or may constitute thesmallest of the particle sizes of the media which are able to find theirway through the coarser meshes 22. These extremely small fines will beretained on the fine mesh 54 until flushed from the system during therinse cycle to be described below.

The housing 40 also includes an elongate cylindrical chamber 56 whichopens to one side of the housing and extends through most of the widthof the housing. A cylindrical valve body 58 is positioned in the chamber56. The diameter of the valve body 58 is somewhat less than the diameterof the chamber 56, as seen in FIGS. 1-3, so that the surface 60 of thecylindrical chamber 56 will be spaced somewhat from the surface 62 ofthe valve body to provide an annular clearance for fluid flow and sealsas will be described below.

A shaft 64 extends from the end of the valve body 58 through an opening66 in the housing 40 and a control knob 68 is mounted on the shaft 64for rotation of the valve body to its various operative positions aswill also be described below.

An axially extending passage 70 extends from the end of the valve bodyopposite the shaft 64 to well within the valve body and adjacent theshaft 64, as best seen in FIGS. 1-3. A plurality of various ports extendradially from the axial passage 70 and outwardly through the valve bodysurface 60. These ports include a first port 72, as best seen in FIGS.1, 4A and 4B, a second port 74 as best seen in FIGS. 2, 4B and 4C, athird port 76 as best seen in FIGS. 3 and 4C, a fourth port 78 as bestseen in FIGS. 2, 4B and 4C, and a fifth port 80 as best seen FIGS. 3 and4C.

The housing 40 also includes a plurality of passages at least some ofwhich communicate with some of the aforementioned ports, depending uponthe position to which the valve body 58 has been rotated. These passagesinclude a first passage 82, a second passage 84, a third passage 86, afourth passage 88, a fifth passage 90 and a sixth passage 92. A passage94 in the housing 40 also communicates with the well 42 and upstreamside of the mesh 54 for the discharge during the rinse cycle of anyfines that may have accumulated on the mesh. Where the fluid treatmentunit includes as one of its treatment media an ion exchange medium resinas a water treatment medium as previously described, it is preferredthat the unit also include a container 96 for the production andcontainment of a brine regeneration composition, such as sodium orpotassium chloride, for the regeneration of the ion exchange medium. Thefifth and sixth passages 90 and 92 preferably communicate with thecontainer 96 to introduce water to the container to produce the brineand to discharge the brine from the container during backwash andregeneration. An overflow conduit 97 is preferably provided in thecontainer 96 and communicates with still another passage 98 through thehousing 40 to discharge any excess brine solution.

Several O-rings 100, 101 and 102 also preferably encircle the valve body58 and are spaced from each other along the length of the valve body asseen in the drawings. O-rings 101 and 102 separate the overallcylindrical surface 62 of the valve body 58 into a first area 104 which,due to the spacing of the valve body surfaces 62 from the chambersurface 60, defines a first annular passage 106 between the chambersurface 60 and valve body 58 as seen in FIGS. 1-3. The O-rings 100 and101 define a second area 108 on the surface 62 of the valve body 58,which second area also defines a second annular passage 110 about thevalve body, as seen in FIGS. 1-3. O-ring 102 also defines a third area112 on the surface 62 of the valve body 58.

The valve assembly also preferably includes a nipple 116 for coupling toa source of water supply (not shown) to communicate the water to betreated to the axial passage 70 in the valve body 58, as shown in thedrawings. The nipple 116 preferably includes one or more O-rings 118 onthe end of the nipple which is positioned in the housing cylindricalchamber 56 to seal the nipple against leakage. The nipple 116 may alsoinclude a conventional annular flange 120 which is adapted to seatagainst the end of the housing 40 and be held there by a threaded cap122.

A number of blind seals are also positioned on the cylindrical surface62 of the valve body 58 at various locations and in various ones of itsareas as best seen in FIG. 4. These blind seals are shown in FIG. 4 insolid black, and they are termed “blind” because they do not communicatewith any port in the valve body. This is in contrast to “port” sealswhich are shown in outline only in FIG. 4 of the drawing and whichsurround various of the previously identified ports through the valvebody 58.

Referring to FIGS. 1 and 4A in which the valve body 58 is shown in itsservice position, blind seals are shown in blocking arrangement withpassages as follows: blind seal 124 in the third area 112 of the valvebody blocks the fifth passage 90, blind seal 126 also in the third area112 blocks the sixth passage 92, blind seal 128 in the first area 104 ofthe valve body blocks the passage 98 from the overflow conduit 97 incontainer 96, and blind seal 130 also in the first area 104 blocks thepassage 94, while port seal 132 in the first area 104 is in alignmentwith the first passage 82 to communicate it with port 72. Thus, when thevalve body 58 is in its service position as shown in FIGS. 1 and 4A,water will be communicated from the nipple 116 through passage 70, port72, port seal 132 and the first passage 82 upwardly through the riser30. The water is discharged from the top of the riser onto the fine mesh36 which will retain undesirable particulate contaminates. The waterwill then pass through the mesh 36, the perforations 20 and the floor 18of the top piece 34, and will flow serially down through the media A, B,C, D in the chambers 21 of the respective containers 12, 13, 14 and 15.The treated water will continue to flow downwardly through the mesh 54which will retain any super fine particulates, the perforations 52 inthe floor plate 48, through the second passage 84, around the valve body58 in its second area 108 and second annular passage 110, and outthrough the third discharge passage 86 to service. In this serviceposition of the valve body 58, flow will be blocked through the fifthpassage 90 by blind seal 124, the sixth passage 92 by blind seal 126,the passage 98 by blind seal 128 and the passage 94 by blind seal 130.

Referring to FIGS. 2 and 4B, when it is desired to shift the operationof the unit from the service mode to the rinse mode, the valve body 58is rotated 90° to the rinse position, as shown in FIG. 4B. This willrotate a blind seal 134 in the third area 112 into blocking relationshipwith the sixth passage 92 from the container 96, and a blind seal 136 inthe second area 108 into blocking relationship with the second passage84 from the multimedia fluid treatment unit. This 90° rotation to therinse position also rotates blind seal 128 in the first area 104 out ofblocking relationship to the passage 98 from the overflow conduit 97,which permits it to communicate via the first annular passage 106 aroundthe valve body to the fourth drain passage 88 to discharge any overflowfrom the container 96 to drain. The blind seal 130 in the first area 104is also rotated out of blocking relationship to the passage 94 whichpermits flushing of the mesh 54 through passage 94 and through the firstannular passage 106 around the valve body to the drain 88 to remove anyfines which may have collected on the mesh 54. Rotation of the valvebody 58 to the rinse position as shown in FIGS. 2 and 4B also alignsport seal 138 in the first area 104 with the first passage 82 to permitrinse water to pass from the passage 70 through the second port 74, thefirst passage 82 and the riser 30 to flush the media A, B, C and D asshown by the arrows in FIG. 2. Rotation of the valve body to the rinseposition shown in FIGS. 2 and 4B also aligns the port seal 140 in thethird area 112 with the fifth passage 90 to introduce water through theport 78 and passage 90 to the container 96 to produce liquid toregenerate an ion exchange medium which may be in the unit.

Referring now to FIGS. 3 and 4C, when it is desired to shift theoperation of the unit to backwash and regenerate the media, the valvebody 58 is rotated an additional 90° from the rinse position or 180°from the service position. In this backwash position, a blind seal 142in the first area 104 will be rotated into sealing relationship with thepassage 94, a blind seal 144 in the third area 112 will be rotated intosealing relationship with the fifth passage 90, and a blind seal 146 inthe first area 104 will be rotated into sealing relationship with thepassage 98 from the overflow 97 of the container 96. At the same time, aport seal 148 in the second area 108 will be rotated into alignment withthe second passage 84 to communicate passage 70 and the third port 76with the passage 84 and the bottom side of the respective water treatingmedia to backflush the media in the reverse direction. Port seal 150will also be aligned with the sixth passage 92 to discharge theregenerating fluid from the container 96 to passage 92 and the fifthport 80 through the passage 70 and to the bottom side of the watertreating media. Finally, in this backwash position, port seal 138 willalso be rotated out of alignment with the first port 82 so that thebackflushing liquid which has passed upwardly through the media D, C, Band A in that order, will pass downwardly through the riser 30, throughthe passage 82 into the first annular passage 106 around the valve body,and out through the fourth drain passage 88.

From the foregoing, it will be appreciated that the servicing of theunits of the present invention is greatly facilitated and their lifesubstantially prolonged both by virtue of the beneficial effect of thevarious media on each other, e.g. removal of detrimental chlorine fromthe incoming water which might otherwise shorten the life of an ionexchange medium and/or activated carbon. Life of the unit and the mediawithout servicing is also substantially extended by the ability to beable to rinse, backwash and regenerate the media rather than merelydiscarding it when it has completed its first service cycle.

It will be appreciated that although the embodiment of the unit is shownin the drawings with a riser 30, the riser may be eliminated as well asthe openings through the floors of the respective containers whichaccommodate the riser, and the containers may themselves be placed in ahousing which may be flooded in lieu of the riser.

It will also be appreciated that although the valve body is described asrotated 90° between its several positions, the actual number of degreesof rotation is not critical to the invention.

It will also be understood that the preferred embodiments of the presentinvention which have been described are merely illustrative of theprinciples of the present invention. Numerous modifications may be madeby those skilled in the art without departing from the true spirit andscope of the invention.

I claim:
 1. A rotatable valve comprising: a housing having an elongatecylindrical chamber therein; first, second, third and fourth passagesextending through said housing and communicating with said chamber; acylindrical valve body mounted for rotation in said chamber, said valvebody having an axially extending passage therein, said axially extendingpassage communicating with a source of fluid supply for the valve, saidvalve body having a first area adjacent its cylindrical surface which isaligned with said first and fourth passages, and a second area alsoadjacent its cylindrical surface which is aligned with said second andthird passages, said valve body also including first and second portscommunicating between said axially extending passage and said first areaand a third port communicating between said axially extending passageand said second area; said cylindrical valve body being selectivelyrotatable between either of at least three positions including, a firstposition in which said first port communicates with said first passageand said second passage communicates with said third passage, a secondposition in which said second port communicates with said first passage,and a third position in which said third port communicates with saidsecond passage and said first passage communicates with said fourthpassage.
 2. The rotatable valve of claim 1, wherein said second passageis sealed when said cylindrical valve body is rotated to said secondposition.
 3. The rotatable valve of claim 2, wherein the sealing is by aseal on the surface of said valve body in said second area which alignswith said second passage when said valve body is rotated.
 4. Therotatable valve of claim 1, wherein the surface of the cylindrical valvebody in said first and second areas is spaced from the surface of saidchamber to define an annular passage between said surfaces, and saidfirst and second areas are divided from each other to define first andsecond annular passages at said first and second areas respectively. 5.The rotatable valve of claim 4, wherein said first and second areas aredivided from each other by an O-ring about said cylindrical valve bodyto define said first and second annular passages.
 6. The rotatable valveof claim 1, wherein said cylindrical valve body comprises a singlecylinder.
 7. The rotatable valve of claim 1, including fifth and sixthpassages extending thorough said housing and communicating with saidchamber; said cylindrical valve body having a third area adjacent itssurface which is aligned with said fifth and sixth passages, and fourthand fifth ports communicating between said axially extending passage andsaid third area; and wherein said fifth passage communicates with saidfourth port when said cylindrical valve body has been rotated to saidsecond position, and said sixth passage communicates with said fifthport when said cylindrical valve body has been rotated to said thirdposition.
 8. The rotatable valve of claim 7, wherein said fifth andsixth passages are sealed when said cylindrical valve body is rotated tosaid first position, said sixth passage is sealed when said cylindricalvalve body is rotated to said second position, and said fifth passage issealed when said cylindrical valve body is rotated to said thirdposition.
 9. The rotatable valve of claim 8, wherein the sealing is byseals on the surface of said valve body in said third area which alignwith said fifth and sixth passages when said valve body is rotated. 10.The rotatable valve of claim 7, wherein the surface of the cylindricalvalve body in said third area is also spaced from the surface of saidchamber, and said first, second and third areas are divided from eachother to define first and second annular passages at said first andsecond areas, respectively.
 11. The rotatable valve of claim 10, whereinsaid first, second and third areas are divided from each other byO-rings about said cylindrical valve body to define said first andsecond annular passages.
 12. The rotatable valve of claim 7, including aseventh passage extending through said housing and communicating withsaid first area, said first area being aligned with said seventhpassage; and wherein said seventh passage communicates with said fourthpassage when said cylindrical valve body has been rotated to said secondposition.
 13. The rotatable valve of claim 12, wherein said seventhpassage is sealed when said cylinder is rotated to said first and thirdpositions.
 14. The rotatable valve of claim 13, wherein the sealing isby a seal on the surface of said valve body in said first area whichaligns with said seventh passage when said valve body is rotated. 15.The rotatable valve of claim 1, including in combination therewith aunit containing at least one fluid treatment medium, said first andsecond passages communicating with said medium, said third passagecomprising a discharge for fluid which has been treated by the medium,and said fourth passage comprising a drain, and wherein said firstposition comprises a service position in which the fluid is treated inthe unit by the medium, said second position comprises a rinse positionin which the treatment medium is rinsed, and said third positioncomprises a backwash position in which the treatment medium isbackwashed.
 16. The rotatable valve of claim 15, wherein said treatmentmedium includes an ion exchange medium, and said backwash positionregenerates said ion exchange medium.